Phase behavior of krypton and xenon to 50 GPa

The fcc-hcp phase transitions of krypton and xenon were investigated using synchrotron angle dispersive x-ray diffraction in a diamond-anvil cell up to 50 GPa. Both gases, heated at the highest pressures, exhibit coexistence of the fcc and hcp phases upon decompression to nearly ambient conditions with a decreasing hcp/fcc ratio.